[Homeoproteins: participation in hematopoietic processes?]

The molecular basis of commitment and differentiation of hematopoietic cells remain poorly understood at the genetic level. Among putative candidates involved in these processes are homeoproteins, a large family of transcription factors which play a major role during development. Using a strategy based on the polymerase chain reaction (PCR) we have isolated nine different Antennapedia-like homeobox (HOX) genes from purified human hematopoietic precursors. Their expression patterns, analyzed with a panel of leukemia-derived cell lines representing various blood cells phenotypes, appears to be lineage-restricted. Extending our study to all the known members of the HOX 1 and HOX 2 clusters, we found that HOX 1 genes are predominantly detected within cell of myelomonocytic origin whereas HOX 2 genes transcripts are principally expressed in erythro-megakaryocytic cell lines. Furthermore, we have observed that the expression of three HOX 1 genes within B lymphoid lineages is stage-related and that the expression of several of them is switched off during TPA-induced differentiation of KG1 and U937 cells. These observations support the idea that homeoproteins could be regulators of lineage determination during hematopoiesis.